The postdentary trough is a skeletal feature seen in
Mesozoic mammals. It is found on the inside of the lower jaw (
dentary
In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla).
The jawbone ...
), at the back behind the molar teeth. It is the hollow in which the postdentary bones and
Meckel's cartilage
In humans, the cartilaginous bar of the mandibular arch is formed by what are known as Meckel's cartilages (right and left; also known as Meckelian cartilages), above which the incus and malleus are located. Meckel's cartilage arises from the fir ...
sit. These bones form the middle ear in later mammal groups (see
Evolution of mammalian auditory ossicles
The evolution of mammalian auditory ossicles was an evolutionary process that resulted in the formation of the mammalian middle ear, where the three middle ear bones or ossicles, namely the incus, malleus and stapes (a.k.a. "the anvil, hammer, and ...
); they include the
incus
The ''incus'' (: incudes) or anvil in the ear is one of three small bones (ossicles) in the middle ear. The incus receives vibrations from the malleus, to which it is connected laterally, and transmits these to the stapes medially. The incus i ...
(
quadrate),
malleus
The ''malleus'', or hammer, is a hammer-shaped small bone or ossicle of the middle ear. It connects with the incus, and is attached to the inner surface of the eardrum. The word is Latin for 'hammer' or 'mallet'. It transmits the sound vibra ...
(
articular
The articular bone is part of the lower jaw of most vertebrates, including most jawed fish, amphibians, birds and various kinds of reptiles, as well as ancestral mammals.
Anatomy
In most vertebrates, the articular bone is connected to two o ...
), ectotympanic (
angular) and prearticular.
[Zhe-Xi Luo 201]
Developmental patterns in Mesozoic evolution of mammal ears
Annual Review of Ecology, Evolution, and Systematics, 42, 355-380
In
Mesozoic mammals these bones gradually change position and size until they are incorporated in the middle ear.
References
Mammal anatomy
Evolution of mammals
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